Row Sub Total equals is calculated

OK, taking a look back at the original post, perhaps something like:

Measure 2 =
VAR __Table =
  ADDCOLUMNS(
    SUMMARIZE(
      'Table 3',
      [Group],
      [Attribute],
      "__Measure",[Measure]
    ),
    "__IncludeInTotals",SEARCH("%",[Attribute],,-1)
  )
RETURN
  IF(
    HASONEVALUE('Table 3'[Attribute]),
    [Measure],
    SUMX(FILTER(__Table,[__IncludeInTotals] = -1),[__Measure])
  )